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There is a plugin outlet there called topic-above-footer-buttons

This helps you see them: (deprecated) Plugin outlet locations theme component

Then follow this guide:

Using Plugin Outlet Connectors from a Theme or Plugin

Discourse includes hundreds of Plugin Outlets which can be used to inject new content or replace existing contend in the Discourse UI. ‘Outlet arguments’ are made available so that content can be customized based on the context. Choosing an outlet To find the name of a plugin outlet, search Discourse core for “<PluginOutlet”, or use the plugin outlet locations theme component. (e.g. topic-above-posts). Wrapper outlets Some outlets in core look like <PluginOutlet @name="foo" />. These allow you…